Topic 3 - Redox I

Question 1

Define Oxidation Number

Answer 1

The charge that an ion has or that it would have if the species were fully ionic

Question 2

Give the rules of oxidation number that relate to all elements generally

Answer 2

The ON of an uncombined element is 0
The sum of the ONs in a compound is equal to its overall charge
The more electronegative element in a substance is given a negative ON

Question 3

Give the rules of oxidation number relating to hydrogen, oxygen and fluorine

Answer 3

The ON of F is always -1
The ON of H is always +1, except when combined with a less electronegative element, when it is -1
The ON of O is always -2, except in peroxides, when it is -1, and when with F, when it is positive

Question 4

What is an oxidising agent?

Answer 4

A species that oxidises another species by removing one or more electrons, itself being reduced

Question 5

What is a reducing agent?

Answer 5

A species that reduces another species by adding one or more electrons, itself being oxidised

Question 6

Define disproportionation

Answer 6

The simultaneous oxidation and reduction of an element in a single reaction

Question 7

Define redox

Answer 7

Simultaneous oxidation and reduction in a single reaction

Question 8

What do roman numerals in chemical formulae represent?

Answer 8

The oxidation number of the element it is in brackets next to

Question 9

Form a full ionic equation from:
FeO4 2- + 8H+ + 5e- -> Fe 3+ + 4H2O
C2O4 2- -> 2CO2 + 2e-

Answer 9

2FeO4 2- + 16H+ + 3C2O4 2- -> 2Fe 3- + 8H2O + 6CO2

Question 10

Form a full ionic equation from:
Cr2O7 2- + 14H+ + 6e- -> 2Cr 3+ + 7H2O
Fe 2+ -> Fe 3+ + e-

Answer 10

Cr2O7 2- + 14H+ + 6Fe 2+ -> 2Cr 3- + 7H2O + 6Fe 3-